High-dose radiotherapy could reduce cognitive function for people with low-grade brain tumours
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Dutch authors of a study in this week's issue of THE LANCET caution against the use of high-level radiation for the treatment of low-grade brain tumours-as such treatment does not improve survival and may contribute to cognitive decline. The authors also comment that the tumour itself is the main cause of cognitive impairment, and that other factors-notably the use of antiepileptic drugs-may play a role in reducing cognitive function.
Survival benefits of treatment for gliomas (a type of brain tumour) with radiotherapy are questionable-such treatment can cause substantial damage to the brain over time. Consequently, the best treatment strategy is unclear. Martin Klein from Vrije Universiteit Medical Centre, Amsterdam, Netherlands, and colleagues aimed to identify the specific effects of radiotherapy on objective and self-reported cognitive function, and on cognitive deterioration over time, in patients with low-grade gliomas treated with early radiotherapy.
195 patients (of whom around half had received radiotherapy 1-22 years previously) were compared with 100 patients with low-grade haematological cancers ( who had non-Hodgkin lymphomas or chronic lymphatic leukaemia), and with 195 healthy people (a control group). The investigators aimed to differentiate between the effects of the tumour (eg, disease duration,location within the brain) and treatment effects (neurosurgery, radiotherapy, antiepileptic drugs) on cognitive function and on the relative risk of cognitive disability.
Patients with low-grade gliomas had lower ability in all cognitive areas ( such as perception/psychomotor speed, memory, and attention) than patients with haematological cancer; cognitive ability was further reduced when compared with healthy individuals. Patients given high doses of radiotherapy (more than 2 Gy) had greater memory impairment than patients with brain tumours not given radiotherapy. Antiepileptic drug use was strongly associated with disability in attention and executive function (the capacity for formulating goals and carrying out plans effectively).
Martin Klein comments: "Our results suggest that the tumour is the main cause of cognitive deficits, although low-grade glioma patients treated with early radiotherapy did less well in some cognitive tests than did low-grade glioma patients who had no radiotherapy. The main variable responsible for this difference is the fraction dose size. This observation has implications for the decision to treat low-grade glioma with radiotherapy. Since early radiotherapy in low-grade glioma does not enhance survival, and, moreover, could contribute to cognitive deficits, early radiation should not be applied in asymptomatic patients. If radiation is applied, either as an initial treatment or at a later stage, fraction doses should not exceed 2 Gy. Because the cognitive disturbances in low-grade glioma patients are mainly affected by the tumour itself, and, possibly, by epileptic seizures and/or by antiepileptic drugs, these factors deserve more attention than they have previously received."
Contact: Dr Martin Klein, Department of Medical Psychology, Vrije Universiteit Medical Centre, Van der Boechorststraat 7, 1081 BT Amsterdam, Netherlands; T) 31-20-444-8432; F) 31-20-444-8230; E) email@example.com